1. Field of the Invention
The present invention relates generally to elastomeric seals. More particularly the invention concerns an elastomeric sealing element of unique configuration which is particularly adapted for use in sealing valving assemblies within beverage containers such as beer kegs and the like.
2. Discussion of the Prior Art
Elastomeric material, such as rubber and soft plastic which has been formed into O-rings and like configurations have long been used to sealably interconnect component parts of fluid systems. Frequently the elastomeric sealing member, such as the O-ring, is carried by one component of the system so that upon assembly of the system components the elastomeric member will be axially deformed causing a portion thereof to be urged into pressural engagement with another of the components thereby providing a fluid seal between the components.
While elastomeric seals have proven effective in performing the sealing function, they are easily damaged by uncontrolled axial and shear forces being exerted on the seals during assembly and disassembly of the fluid systems. High shear forces tend to abrade, deform and otherwise damage the elastomeric material. Uncontrolled axial forces tend to compress the material beyond its elastic limits. This results in excessive "compression set", which is a measure of the inability of an elastomer to return to its original uncompressed state after it has been subjected to actual material compression. If the elastomer once takes a "compression set" its sealing capability is reduced and may have to be replaced if fluid leakage is to be avoided.
Although the sealing element of the present invention is useful in a wide variety of fluid sealing applications, it is particularly useful in sealing valving assemblies to beverage containers, such as beer kegs and the like. For example, in systems for tapping kegs of fluid and particularly containers of beer, a valve assembly is secured to the top of the keg for providing access to the fluid ultimately to be delivered from the keg to a remote location for distribution. Typically, the valve assembly includes a dual valve arrangement with a siphon tube which extends from the valve assembly to the bottom of the keg. The valve assembly is fixed within a valve receiving member to provide a valved access to the fluid once it is pressurized. The valve system, when tapped by a coupler or some other keg tapping means connected to a pressure source, allows pressurized gas to flow into the keg until the desired pressure within the keg is achieved to force the fluid out of the keg through the valve system and ultimately to a distribution device which the fluid can be used to fill glasses and the like.
In many prior art systems the valve assembly is threadably received with the valve receiving member which, in turn, is affixed within an aperture formed in the fluid container. As a general rule, an elastomeric seal of standard configuration is used to prevent fluid leakage between the valving assembly and the valve receiving member. Such an arrangement has resulted in substantial problems.
Two basic problems exist when an elastomeric ring is used as the sealing means between threadably interconnected components. One obvious problem is the potential damage to the elastomer as a result of the shear forces applied to it as the components are rotatably connected and disconnected. The second, and even greater problem, derives from the fact that the torquing of the valving assembly into the receiving member, even at a relatively fixed torque of say 50 foot-pounds, provides very little control over the resulting thrust being exerted on the elastomeric ring. Because of dimensional variations in the components and dimensional variations in the threads, excessive compression of the elastomer can result even under fixed torque conditions. This uncontrolled compression can easily cause compression set which destroys the sealing effectiveness of the elastomeric ring.
It is also to be noted that in a system embodying an elastomeric seal, even effective control over assembly torque does not necessarily provide control over disassembly torque. In point of fact, experience has shown that the only known relationshp between installation and removal torque in a threadable engagement with a pure elastomer seal interposed between metal components is that the removal torque will always be less than the installation torque; but without predictable or quantitative lineal relationship. Tests have shown that a constant installation torque of 50 foot-pounds results in removal torques that vary from 90% down to 25% of the installation torque.
In summary, prior art threaded systems embodying a standard type of elastomer seal are deficient in several critical aspects. In such systems, the elastomeric seal is exposed to uncontrolled thrust, high shear, uncontrolled deformation or compression, as well as uncontrolled removal torques.
As will be apparent from the discussion which follows, the novel sealing element of the present invention overcomes all of the aforementioned disadvantages of the prior art.